In a network environment, data generated by a workstation may be stored on a remote device. The data storage device is connected to the workstation by a network that is external to the workstation and may be used by a number of devices. A Storage Area Network, hereafter referred to as a “SAN”, consists of initiators, typically workstations or servers, and targets, such as a disk drive array or tape library. Each component of a SAN has an address which allows network storage traffic to be routed to and from the appropriate end nodes.
SANs may comprise a number of Serial Attached SCSI (SAS)-based or Serial Advanced Technology Attachment (SATA)-based target devices. The computer bus interface for connecting to SAS and SATA storage is referred to collectively herein as “SAS/SATA.” SAS and SATA-based target devices, including without limitation disk drives, tape drives, solid-state drives, optical storage and protocol expanders, may be connected to a SAN via a storage router which provides protocol translation and target device aggregation. Storage routers, also commonly known as protocol bridges or gateways, are responsible for mapping target devices into the SAN namespace in order to provide seamless connectivity between initiators and targets.
On the SAN, the storage router exposes a number of targets, each target having one or more Logical Units (LUNs). LUNs can represent a single physical device or a logical device created by the concatenation of storage from several different physical devices. A target identifier uniquely identifies each target on the SAN. Some examples of target addresses are Fibre Channel worldwide name (WWN), iSCSI Qualified name (iQN) or Infiniband EUI-64. Mapping of physical devices to SAN target identifier and LUN identifier is the responsibility of the storage router, and may be configured manually by the user or automatically by the storage router.
SAS and SATA target devices are often housed in physical enclosures along with a SAS expander. A SAS expander communicates with multiple SAS devices, allowing a single initiator port to connect with multiple SAS targets. Target devices in the enclosure are identified by a slot number known to the SAS expander. The storage router, acting as a SAS initiator, can discover the target's slot number by querying the expander using the Serial Management Protocol (SMP) or SCSI Enclosure Services (SES).